91Ó°ÊÓ

A satellite to reflect radar is a $2.0-m-$diameter, $2.0-mm-$thick spherical copper shell. While orbiting the earth, the satellite absorbs sunlight and is warmed to $50°\mathrm{C}$. When it passes into the earth's shadow, the satellite radiates energy to deep space. The temperature of deep space is actually $3\mathrm{K}$, as a result of the Big Bang 14 billion years ago, but it is so much colder than the satellite that you can assume a deep-space temperature of $0\mathrm{K}$. If the satellite's emissivity is $0.75$, to what temperature, in ${}^{∘}\mathrm{C}$, will it drop during the 45 minutes it takes to move through the earth's shadow?

The sun's intensity at the distance of the earth is $1370\mathrm{W}/{\mathrm{m}}^2$. $30\%$of this energy is reflected by water and clouds; $70\%$ is absorbed. What would be the earth's average temperature (in ${}^{∘}\mathrm{C}$) if the earth had no atmosphere? The emissivity of the surface is very close to 1 . (The actual average temperature of the earth, about $15°\mathrm{C}$, is higher than your calculation because of the greenhouse effect.)

In Problems 74 through 76 you are given the equation used to solve a problem. For each of these, you are to

a. Write a realistic problem for which this is the correct equation.

b. Finish the solution of the problem.

74.$50\mathrm{J}=-n(8.31\mathrm{J}/\mathrm{molK})(350\mathrm{K})\ln \left(\frac{1}{3}\right)$

In Problems 74 through 76 you are given the equation used to solve a problem. For each of these, you are to

a. Write a realistic problem for which this is the correct equation.

b. Finish the solution of the problem.

75. $\left(200×{10}^{-6}{\mathrm{m}}^3\right)\left(13,600\mathrm{kg}/{\mathrm{m}}^3\right)×(140\mathrm{J}/\mathrm{kgK})\left(90°\mathrm{C}-15°\mathrm{C}\right)$

$+(0.50\mathrm{kg})(449\mathrm{J}/\mathrm{kgK})\left(90°\mathrm{C}-T_{\mathrm{i}}\right)=0$

In Problems 74 through 76 you are given the equation used to solve a problem. For each of these, you are to

a. Write a realistic problem for which this is the correct equation.

b. Finish the solution of the problem.

76.$(10\mathrm{atm})V_2^{1.40}=(1.0\mathrm{atm})V_1^{1.40}$

10 g of aluminum at 200°C and 20 g of copper are dropped into 50 cm3 of ethyl alcohol at 15°C. The temperature quickly comes to 25°C. What was the initial temperature of the copper?

A beaker with a metal bottom is filled with $20\mathrm{g}$of water at $20°\mathrm{C}$. It is brought into good thermal contact with a $4000{\mathrm{cm}}^3$container holding $0.40\mathrm{mol}$of a monatomic gas at $10atm$pressure. Both containers are well insulated from their surroundings.

What is the gas pressure after a long time has elapsed? You can assume that the containers themselves are nearly massless and do not affect the outcome.

III FIGURE CP19.79 shows a thermodynamic process followed by $0.015mol$of hydrogen. How much heat energy is transferred to the gas?

Draw a first-law bar chart (see Figure 19.12) for the gas process in

Shows two different processes taking an ideal gas from state i to state f.

a. Is the temperature change ∆T during process A larger than, smaller than, or equal to the change during process B? Explain.

b. Is the heat energy added during process A greater than, less than, or equal to the heat added during process B? Explain.